Method and apparatus for air separation of diatomaceous earth milling



Oct. 22, 1935. McKlNLEY STOCKTON 2,018,039 METHOD AND APPARATUS FOR AIR SEPARATION OF DIATOMACEOUS EARTH MILLING Filed July 23, 1932 25 a/ 26 4 Z 7 W a; w

( k KI INVENTOR. Mlf/N; E r Srocxron;

ATTORNEY,

Patented Oct. 22, 1935 amatsa METHOD AND APPARATUS FOR AIR SEP- ARATION F DIATOMACEOUS EARTH MILLING McKinley StocktornLos Angeles, Calif., assignor to The Dicalite Company, Los Angeles, Calif... a corporation of Delaware Application July 23, 1932, Serial No. 624,306

7 Claims.

This invention relates to machinery for classifying diatomaceous earth and the like, and particularly pertains to an air classifier for such purpose, and the method of using the same.

Beds of diatomaceous earth suitable for commercial operations usually contain bands of hard dark colored silica termed flint rock, nodules of more or less hardened concretions resembling shale, and a small percentage of sand. In mining or quarrying diatomaceous earth every effort is made to eliminate these impurities, but it has heretofore been found to be impossible to completely separate the impurities from the desirable earth. It is highly desirable in the milling of diatomaceous earth to remove these objectionable particles, as they are a great source of trouble when present in any product, whether used as a filtration medium, as a filler, or for other purposes.

It is the principal object of the'present invention to provide a method of operation and means whereby the undesirable particles of rock, nodules of hardened concretions and particles of sand may be readily separated from the desired finished product, and may be effectually rejected so that they will not again commingle with the product and so that in the particular operation with dis.- tomaceous earth a product of uniform character may be obtained.

The present invention contemplates the pro vision of suitable diatomaceous earth milling machinery delivering its comminuted material to air separation means within which the desired and rejected particles will be suspended in a fluid medium and will gravitate in such manner as to insure that objectionable particles will be competely rejected from the material passing through the apparatus.

The invention is illustrated by way of example in the accompanying drawing, in which:-

The figure is a view in vertical section showing a diagram of the apparatus with which the pres-' ent invention is concerned.

Referring more particularly to the drawing, It indicates a. conduit through which comminuted diatomaceous earth and associated particles are delivered to a vertical pipe II, the lower end of which pipe is suitably connected with a centrifugal blower I3. The upper end of the vertical pipe I l communicates directly with an air classifier H which has a frusto-conical section l5 terminating at its upper enlarged end in a cylindrical shell IS. The upper end of the shell I6 is closed by a conical top section I! through the apex of which a main eduction pipe 18 extends, The longitu- (CIL 209-138) dinal axis of the eduction pipe 88 is coincident with the vertical axis of the classifierv l4 and the longitudinal center line of the inlet pipe H.

Mounted within the main shell of the classifier and spaced therefrom is a separating cone [9. 5 The upper end of this separating cone member comprises a cylindrical portion 20 entirely opened at its upper edge. The cylindrical wall is concentric with the outer cylindrical shell l6 and is spaced therefrom to form an annular vertical passageway 2! between the classifying member 89 and'the shell. The lower end'of the eduction pipe l8 projects a suitable distance into the mouth of the cylindrical portion 2!] of the classifying member and since it is arranged in concentric relation to the cylindrical portion 20, an annular passageway 22 will be provided as a continuation of the passageway 2|, so that materials in fluid suspension will be carried upwardly within the shell along the annular passageway 2i and into the mouth of the classifying member it through the annular passageway 22. I

This arrangement ensures that the material which is being carried through the apparatus will be given a complete reversal of direction of travel, 25 since it will make a turn of 20 as it passes over the edge of the mouth of the cylindrical portion 20, and then passes upwardly through the eduction pipe 58. The areas of the annular passageways 2! and 22 and the area of the passageway through the eduction pipe it are so proportioned as to insure that heavy particles such as flint, shale and sand will continue to travel under the, force of its gravity and the additional force of gravity toward the bottom of the classifying elemerit i9, and will not make the turn into the eduction pipe 88. This heavy material then flows downwardly into the restricted inverted conical throat 23 of the classifying unit 19 and into a drawoif pipe 24 which extends through the side wall of the shell and communicates with the upper end of a tailings separator 25.

This separater includes a conical bonnet 26, the apex of which directly connects with the drawoff pipe 24, and the base of which conical member is provided with a cylindrical shell 21. Shell 21 telescopes into a cylindrical member 28 which terminates in an inverted conical portion 29, the apex of which is opened as indicated at 30 to permit the finally rejected material to fall from the separator.

A suction pipe 3| extends into the upper cylindrical portion 21 of the second separator and has a down-turned portion 32 which projects into the mouth of the lower cone 29 and is disposed eccentrically thereto. The pipe 3i connects with the pipe It and a flow of air therethrough is caused by the blower it as it-draws the iced supply through the pipe ill and forces it upwardly through the pipe it.

The cylindrical portions 2? and it of the two sections of the tailings separator telescope one within the other and may be adjustably set by suitable set screws 33, thus varying the extent of contact of the heavy grains with the air stream drawn through discharge opening 36 and permitting all the light material to be removed from the heavy grains and returned to the main classifier I 4 without returning any of the heavy grains.

In order to regulate the velocity of air flow through various parts of the apparatus a suitable damper 35 may be placed in the draw-oil? pipe 24, and a damper 36 may be placed in the suction pipe 3|. This provides additional adjustment and control of the air velocity through the tailings separator for the proper suspension of the materials therein. It is also desirable to provide a telescoping joint for the eduction pipe ID at the upper end of the main classifier so that it may be adjustably telescoped into the mouth of the classifying unit l9, making it possible to accurately select a desired grade of product or to accommodate products having different characteristics. Attention is directed to the fact that while this apparatus has been described as operating on fluid'pressure applied to the induction end of the main classifier it might prove highly desirable in some instances to reverse the ar rangement and cause the air to travel through the apparatus under action of suction applied to the eduction pipe it. This, of course, could be done without departing from the spirit of the present invention.

The air drawn into the apparatus may be first passed through a suitable air heating furnace l0 and may thereafter be drawn along the pipe in to receive the material. to be treated from a suitable hopper 4| having a valve'seal 52. It has been found that in a suspending medium of heated air separation of the particles of earth is more readily ailected than when cold air is used and that the tendency of the earth to agglomerate or ball is avoided. The temperature of the air may be varied, but it has been found that amaximum temperature of 600 F, is quite suitable for present purposes.

In operation of the present invention, a material to be classified, specifically diatomaceous earth is delivered to the induction pipe ill in a of air from which blower creates an upwardly flowing stream of air within the pipe it and causes the particles of the material. delivered through pipe lll'to be suspended therein and ele vated thereby. During this elevation, turbulence in the blower tends to disperse the agglomerate material and to separate particles which vary in gravity. The air pressure developed by the blow or may approximately determined, but it has been found that a blower having a capacity of 12,000 cu. ft. of air per minute is adequate for present purposes in the treatment of diatoma ceous earth.

As the air travels upwardly at high velocity it projects the particles of greater density against the cover member Hi, and as the air makes a turn of 180 as it passes over the lip of the cylindrical member 20, the heavy materials move downwardly at a greater rate of speed than the 10 lighter materials, since their speed of travel is accelerated by the action of gravity. The air is then given a reverse turn of 180 so that it follows a sinuous path of travel in reverse directions, first over the lip of the cylindrical member 20 and then around the edge of the eduction pipe I8 and into the vertical passageway there-' through. The lighter solid particles are carriedv upwardly through the pipe l8 since the gravity effect is insuflloient to overcome the velocity of 20 the air .stream in which they are suspended. These lighter particles are in the present instance the desired product.

The heavier tailings fall of their own weight into the inverted cone 23. of the classifying unit 25 Is, this movement being accelerated by a flow of air downwardly through the relatively restricted draw-oil pipe 24. This efiect may be controlled and varied by the operation of dampers 35 and 36. Further controls are provided 30 v by the adjustable relationship of the eduction pipe Hi to the cylindrical portion 20 of the separator IS, by the relative adjustability of the two sections of the tailings separator. In practice it has been found. that by proper adjustment of the 35 various elements, substantially all of the undesired extraneous matter may be rejected from the supply of the product being fed into the an paratus, and. that a substantially uniform product may be drawn oil through the eduction pipe 40 I8. It is to be further pointed out that variations in temperature of the product being treated and the velocity with which it is carried through the apparatus may act to produce different final 4,5 products, and such variations are here contemplated if desired.

It will thus be seen that by the use of the apparatus here disclosed in the manner set forth, it is possible to rapidly and continuously classify materials either to recover the lighter fraction of material or the heavier particles if desired.

While I have shown the preferred form of my invention and a method of operation, it is to be understood that various changes might be made in the combination, construction and arrangement of the parts, and that variation might be made in the steps of the method without departing from the spirit of the invention as claimed.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. Apparatus for the separation of heavy granular particles from comminuted diatomsceous earth, comprising: a primary separator adapted to efl'ect an initial separation of said as granules from a column of air carrying said earth. in suspension and. having an interior chamber adapted to collect said granules; means for in troducing said air and said earth into said primary separator; a blower arranged to maintain to said. air column in motion; a secondary separator comprising a shell having anoutlet for said grain ules from. the lower part thereof; a channel ar ranged to permit said granules to iiow by gravity from said interior chamber of said primary sepu arator into the upper part of said secondary separator, and means for causing a'secondary air stream to enter said secondary separator through said granule outlet and in counterflow to said granules and for causing said secondary air stream to leave said secondaryseparator at a level intermediate its ends and to return to the intake end of said primary separator.

2. Apparatus substantially as and for the purpose set forth in claim 1, in which said last means comprises a channel affording communication between the interior of said secondary separator and the suction of said blower.

3. Apparatus substantially as and for the pur-- pose set forth in claim 1, in which saidsecondary separator is a cylindrical vessel having a conical bottom, said outlet being formed by truncating said cone.

4. Apparatus substantially as and for the purpose set forth in claim 1, in which the shell of said secondary separator consists of mating cylindrical portions arranged to telescope and thus to adiustably vary the vertical distance between said outlet for granules and the point of admission 'of said granules.

5. Apparatus substantially as and for the purpose set forth in claim l, including valve means in said channel for the flow of granules.

6. Apparatus substantially as and for the purpose set forth in claim 1, in-which last said means comprises a channel affording communication between the interior'of said secondary sep arator and the suction of said blower, and including valve means in said communication channel.

7. Apparatus for air classification of diatoms.-

ceous earth comprising: a substantially closed 10 and vertically arranged'outer shell having a conical bottom; an inner shellhaving a conical bottom and an open top, said inner shellv being spaced from and concentric with said outer shell;

a conduit connected to the lower end of said out- 16 er shell; means for feeding material to said conduit; a blower within saidsconduitto comminuto the material entering said outer shell and arranged to maintain a slight superatmospheric pressure within said shells; a channel arranged so 

